Specific heat capacity

Question 1

What is the definition for specific heat capacity?

Answer 1

The specific heat capacity of a substance is the amount of energy needed to raise the temperature of 1kg of the substance by 1K.

Question 2

How do you measure specific heat capacity?

Answer 2

1) Heat the substance with electric heater. Need temperature rise of about 10K to get an accurate value of c.
2) With an ammeter and voltmeter attached to heater find energy supplied.
3) Put data into E = m * c * temp

Question 3

How and why will the value for c be wrong?

Answer 3

It will be too high because some of the energy from heater is transferred to the air and the container.

Question 4

How would you ensure c is an accurate value?

Answer 4

Start below and finish above room temperature to cancel out gains and losses.

Question 5

How can you estimate c of a metal block using the method of mixtures?

Answer 5

1) Heat metal block of known mass, m(b), up to temp T(b)
2) Quickly transfer block into a container containing a mass of water, m(w), at a temperature of T(w)
3) The hot block will heat the water. Measure the temperature of the water once it has reached a steady value, T(s)
4) The energy gained by the water is equal to the heat lost by the block, so
m(w)c(w)temp(w) = m(b)c(b)temp(b)
5) Rearrange for c(b)